Start by googling "volvo V50 ECU tuning" and you'll find plenty of performance parts. Most chips do the same things - they vary in price based on the loader features. Exhaust would start with a 3" downpipe. replacing the muffler/resonator mostly = loud not power. I'd also look for larger sway bars and a strut tower brace, then wheels. After that, the law of diminishing returns weigh heavy.